Biology Definitions

Bio Definintions 

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HOMEOSTASIS

The ability of a system or living organism to adjust its internal environment to maintain a stable equilibrium. 

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TROPISM

Directional resposnes by plants to stimuli form environment.

Include:  Phototropism and Geotropism

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METABOLISM

Sum of physical and chemical processes occurring within a living organism

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POLLINATION

Moment a pollen grain, released from anther lands on stigma of (normally) another flower. 

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FERTILISATION

Moment the nuclei of pollen grain and ovule fuse together

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MENSTRUAL CYCLE

Series of changed in endometrium in preparation for possible implantation of a fertilized ovum.

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MENSTRUATION

The uterus lining breaks down and eventually passes out through the ******

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WHY DOES PLACENTA ACT AS EXCRETORY ORGAN?

Feotus' kidneys are not yet functioning and so foetus is unable to excrete all toxins which will poison the body if not removed.

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HOW IS DEVELOPING FETUS PROVIDED WITH NUTIRENTS

Transfer from mother's blood in placenta via membranes separating blood of mother and foetus and transfer into chronic villi and then into the umbilical vein to foetus along with oxygenated blood. 

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DOMINANT

An allele that is always expressed if present in an individual

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RECESSIVE

An allele that will only be expressed if there are no other versions of the gene present

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HOMOZYGOUS

An individual who has two copies of the same allele

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HETEROZYGOUS

An individual who has more than one different allele present

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CO DOMINANCE

A condition in which both alleles of a gene pair in a heterzygote are fully expressed. 

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MITOSIS

  • Interphase
  • Prophase
  • Metaphase
  • Anaphase 
  • Telophase
  • In
  • Portugal
  • Milan 
  • Are 
  • Televised
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MUTATION

Is the change in the DNA of a cell.

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EVOLUTION

The gradual change in the range of organisms on the Earth

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NATURAL SELECTION

The mechanism by which new species arise through evolutionary changes

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SELECTIVE BREEDING

By carefully controlling which examples of a species are allowed to mate, humans are able to rapidly change the average phenotype to obtain only those individuals with desirable features. 

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